1. Field of Invention
The present invention relates generally to an electro-optical glazing structure having total-reflection and semi-transparent and totally-transparent modes of operation which are electrically-switchable for use in dynamically controlling electromagnetic radiation flow in diverse applications.
2. Brief Description of the Prior Art
The use of windows in homes, commercial buildings, and automotive vehicles alike is very well known. The reasons for providing windows in such structures and systems are directly related to the functions they perform. For example, window structures provide for ventilation, lighting, a sense of spaciousness, as well as a way of making contact with the outdoors. Windows made of glazing (e.g. glass material) also permit selective transmission of electromagnetic radiation between the outdoors and the interior space of homes, commercial buildings, and automotive vehicles. While conventional forms of glazing serves many useful functions, such forms are not without problems.
An appreciation of the problems presented by the use of conventional glazing in windows, can be most easily attained by recognizing the nature and composition of electromagnetic radiation with which windows universally come in contact.
On a clear day at sea level, electromagnetic radiation is composed of 3% ultraviolet light (i.e. electromagnetic radiation in the UV band), 44% visible light (i.e. electromagnetic radiation in the visible band), and 53% infrared light (i.e. electromagnetic radiation in the IR band). In accordance with the laws of physics, 50% of all electromagnetic radiation produced is left hand circularly polarized (LHCP) while the other 50% thereof is right hand circularly polarized (RHCP). The total electromagnetic radiation striking a window surface is a combination of direct radiation from the Sun and diffuse radiation from the ambient environment. While electromagnetic radiation is broad-band in nature, it is the ultraviolet light component thereof which causes molecular decomposition in various types of plastic material and inorganic dyes, which results in color fading.
When electromagnetic radiation strikes a glass window, three different physical processes occur. Some of the radiant energy is transmitted through the glass; some of the radiant energy is reflected off the glass; and a small portion of the radiant energy is absorbed by the glass. The energy transmitted through the glass window is typically absorbed by furnishings or structures within the interior environment, and often becomes trapped therewithin causing an increase in interior temperature.
Depending on the season, electromagnetic radiation transmitted through glass windows can be either mitigate or worsen the thermal loading imposed upon the heating and cooling systems associated with the glass windows. Consequently, during the hot weather season, it is highly desired to shield windows and sliding glass doors from electromagnetic radiation in order to lessen thermal loading upon cooling systems. During cold weather season, it is highly desired to expose windows and sliding glass doors to electromagnetic radiation in order to lessen thermal loading on heating systems.
In short, it is highly desired to selectively control the transmission of electromagnetic radiation through window structures at different times of the day and year so that thermal loading upon the heating and cooling systems of residential, commercial and industrial building environments can be minimized. By minimizing such thermal loading, power can be used in an economical manner to control the internal temperature of residential, commercial and industrial building environments. Achievement of this goal would impact the natural environment in a positive manner, while improving the quality of life.
With such objectives in mind, great effort has been expended in recent times to improve the ways and means of selectively controlling the transmission of electromagnetic radiation through window structures.
One approach to electromagnetic radiation control involves using a window shade to reduce the transmission of electromagnetic radiation through windows. The most popular type of shade is the window blind. However, as window blind is mounted within the interior of the building or transportation environment, electromagnetic radiation is allowed transmit through the window, raise the temperature within the internal environment, and thus increase thermal loading on cooling systems during the hot weather season. Also, the operation of window blinds requires mechanical or electromechanical controls which tend to be bulky and expensive to manufacture, install and maintain.
Another approach to electromagnetic radiation control involves the use of sun control films which are physically applied to the surface of glass windows in building and automotive vehicles alike. Presently a variety of different types of sun control film are marketed by various firms. Such electromagnetic control films can be categorized into one of the three basic categories, namely: high reflectivity film; heat saving or winter film; and fade protection film.
High reflectivity electromagnetic films are most effective at blocking summer heat. The higher the reflectivity of electromagnetic film, the more effective it will be at blocking electromagnetic radiation. Electromagnetic reflectivity film having a silver, mirror-like surface is more effective in blocking electromagnetic radiation than the colored, more transparent films. Electromagnetic reflectivity films can lower the U-value of glass by more than 10%. Notably, in climates having long heating seasons, the use of high reflectivity film prevents using the winter sun to warm the interior of buildings during the cold weather season, and thus lessen thermal loading on building heating systems.
Heat-saving or winter films are designed to reduce winter heat losses through glazing. These films can lower the U-value of glass windows by more than 20%.
Fade-protection films are designed to filter out ultraviolet rays. Ultraviolet rays cause about 60-65% of color fading in most home furnishing fabrics and automobile dash boards.
While electromagnetic radiation control films of the types described above can be used to control heat and glare, eliminate sun damage, and to a lesser extent, reduce visibility into buildings during the daytime. The major disadvantages thereof are reduction in interior light, loss of visibility, and extra care required in cleaning. Moreover, prior art electromagnetic window films are incapable of changing from transmissive during winter months to reflective during summer months in order to effectively use electromagnetic radiation for dynamic temperature control of biological environments (e.g. human habitats, greenhouses and the like).
An alternative approach to electromagnetic radiation control involves using special glass panels having radiation transmission characteristics which effectively absorb (i.e. block) the infrared and ultra violet wavelengths, while transmitting the visible wavelengths thereby allowing window viewing and day light to enter the interior spaces of buildings using such window technology. While the light transmission characteristics of such glass provides a measure of electromagnetic radiation control during cooling seasons, where outdoor temperatures tend to be above 72 degrees Fahrenheit, its IR absorption characteristics prevents, during heating season, IR wavelengths of Sun light to warm the interior spaces of building structures in which such glass panels are installed. Consequently, during heating seasons, such glass fails to lessen the thermal loading on the heating systems of such buildings, as would be desired in an effort to conserve energy and heating resources during the winter months.
In recent times, there has been great interest in using variable light transmission glass or glazing, referred to as xe2x80x9csmart windowsxe2x80x9d, to achieve electromagnetic radiation (i.e. energy) control in buildings and vehicles alike. The reason for using smart window structures, rather than conventional glass window panels, is quite clear. Smart window structures have light transmission characteristics that can be electrically controlled during the course of the day (or year) in order to meet lighting needs, minimize thermal load on heating and/or cooling systems, and provide privacy within the interior spaces of buildings and vehicles alike.
The use of chromogenic switchable glazing or smart windows for controlling the flow of light and heat into and out of a glazing according to occupant comfort, is discussed in great detail in the following papers: xe2x80x9cChromogenic Switchable Glazing: Towards the Development of the Smart Windowxe2x80x9d by Carl Lempert published in the June 1995 Proceedings of the Window Innovation Conference, Toronto, Canada; and xe2x80x9cOptical Switching Technology for Glazingsxe2x80x9d by Carl Lempert published in Thin Solid Films, Volume 236, 1993, pages 6-13, both incorporated herein by reference.
In general, there are several different types chromogenic switchable glazing or smart windows, namely: non-electrically activated switchable glazings; and electrically-activated switchable glazings. The non-electrically activated types of chromogenic switchable glazing are based on: photochromics, thermochromics and thermotropics. The most common electrically-activated types of chromogenic switchable glazing are based on polymer dispersed liquid crystals (PDLC), dispersed particle systems (DPS), and electrochromics.
Prior art smart window structures based upon conventional twisted nematic (TN) or super twist nematic (STN) liquid crystal technology require the use of a pair of polarizers. This, however, results in high optical loss, as up to 60% of the incident light is absorbed by the polarizers, in the desired non-blocking mode of operation.
While a smart window structure based on polymer dispersed liquid crystal (PDLC) technology offers better performance than TN or STN based window structures, such smart window structures suffer from several significant shortcomings. In particular, conventional PDLC panels have a translucent state which can be used only to provide privacy, but lack a totally opaque state and a totally reflective state required for electromagnetic radiation control functions. In addition, the viewing haze limitation provided by the PDLC panels prevents clear viewing through this prior art window structure at larger viewing angles.
A primary drawback associated with Dispersed Particle Systems is that such systems simply do not have a reflection mode of operation, and thus created heat build-up within interior spaces which is sought to be avoided in thermal radiation control applications.
Thus it is clear that there is a great need in the art for an improved form of variable light transmission glazing structure which avoids the shortcomings and drawbacks of prior art technologies.
Accordingly, a primary object of the present invention is to provide an electro-optical glazing structure which avoids the shortcomings and drawbacks of prior art technologies.
Another object of the present invention is to provide an electro-optical glazing structure which has total-reflection, semi-transparent and totally transparent modes of operation for improved control over the flow of electromagnetic radiation within the solar region of the electromagnetic spectrum (i.e. Solar Spectrum).
A further object of the present invention is to provide such an electro-optical glazing structure, in which the modes of operation can be electrically-activated or switched, while avoiding the use of energy absorbing mechanisms.
A further object of the present invention is to provide such an electro-optical glazing structure having a broad band of operation, including the IR, visible and UV portions of the electromagnetic spectrum.
A further object of the present invention is to provide an electro-optical glazing structure, comprising an electrically-active xcfx80-phase retardation panel interposed between a pair of electrically-passive electromagnetic radiation polarizing panels, both of which are capable of reflecting electromagnetic radiation of a certain polarization state, whereby a totally reflective state of operation and a semi-transparent state of operation are provided over the electromagnetic region of the electromagnetic spectrum.
A further object of the present invention is to provide an electro-optical glazing structure, comprising an electrically-active xcfx80-phase retardation panel interposed between a pair of electrically-passive electromagnetic radiation polarizing panels, both of which are capable of reflecting electromagnetic radiation of a linear polarization state, whereby a totally reflective state of operation and a semi-transparent state of operation are provided over the electromagnetic region of the electromagnetic spectrum.
A further object of the present invention is to provide an electro-optical glazing structure, comprising an electrically-active xcfx80-phase retardation panel interposed between a pair of electrically-passive electromagnetic radiation polarizing panels, both of which are capable of reflecting electromagnetic radiation of a linear polarization state, one is parallel to other, whereby a totally reflective state of operation and a semi-transparent state of operation are provided over the electromagnetic region of the electromagnetic spectrum.
A further object of the present invention is to provide an electro-optical glazing structure, comprising an electrically-active xcfx80-phase retardation panel interposed between a pair of electrically-passive electromagnetic radiation polarizing panels, both of which are capable of reflecting electromagnetic radiation of a linear polarization state, one is perpendicular to other, whereby a totally reflective state of operation and a semi-transparent state of operation are provided over the electromagnetic region of the electromagnetic spectrum.
A further object of the present invention is to provide an electro-optical glazing structure, comprising an electrically-active xcfx80-phase retardation panel interposed between a pair of electrically-passive cholesteric liquid crystal (CLC) electromagnetic radiation polarizing panels, both of which are capable of reflecting electromagnetic radiation of a LHCP state, whereby a totally reflective state of operation and a semi-transparent state of operation are provided over the electromagnetic region of the electromagnetic spectrum.
A further object of the present invention is to provide an electro-optical glazing structure, comprising an electrically-active xcfx80-phase retardation panel interposed between a pair of electrically-passive CLC electromagnetic radiation polarizing panels, both of which are capable of reflecting electromagnetic radiation of a RHCP state, whereby a totally reflective state of operation and a semi-transparent state of operation are provided over a broad-band region of the electromagnetic spectrum.
A further object of the present invention is to provide an electro-optical glazing structure, comprising an electrically-active xcfx80-phase retardation panel interposed between a pair of electrically-passive CLC electromagnetic radiation polarizing panels, one of which is capable of reflecting electromagnetic radiation of the LHCP state and the other of which is capable of reflecting electromagnetic radiation of the RHCP state, whereby a totally reflective state of operation and a semi-transparent state of operation are provided over a broad-band region of the electromagnetic spectrum.
A further object of the present invention is to provide an electro-optical glazing structure, comprising an electrically-passive xcfx80-phase retardation panel interposed between a pair of electrically-active CLC electromagnetic radiation polarizing panels, both of which are capable of reflecting electromagnetic radiation of the LHCP state, whereby a totally reflective state of operation and a totally transparent state of operation are provided over a broad-band region of the electromagnetic spectrum.
A further object of the present invention is to provide an electro-optical structure, comprising an electrically-passive xcfx80-phase retardation panel interposed between a pair of electrically-active CLC electromagnetic radiation polarizing panels, both of which are capable of reflecting electromagnetic radiation of the RHCP state, whereby a totally reflective state of operation and a semi-transparent state of operation are provided over a broad-band region of the electromagnetic spectrum.
A further object of the present invention is to provide an electro-optical glazing structure, comprising a pair of electrically-active CLC electromagnetic radiation polarizing panels, one of which is capable of reflecting electromagnetic radiation of the LHCP state and the other of which is capable of reflecting electromagnetic radiation of the RHCP state, whereby a totally reflective state of operation and a totally transparent state of operation are provided over a broad-band region of the electromagnetic spectrum.
Another object of the present invention is to provide an actively-controlled window or viewing panel constructed from the electro-optical glazing structure of the present invention, wherein the transmission of electromagnetic radiation can be dynamically controlled over a broad-band region of the electromagnetic spectrum, between 50% transmission to 100% reflection and between 100% transmission to 100% reflection.
Another object of the present invention is to provide an actively-controlled window or viewing panel constructed from the electro-optical glazing structure of the present invention, wherein the transmission of electromagnetic radiation over the UV and IR regions of the electromagnetic spectrum can be totally reflected, rather than absorbed, reducing the temperature cycle range which the window structure is required to undergo.
Another object of the present invention is to combine the electro-optical glazing panel of the present invention with a controllable scattering layer or structure in order to scatter light transmitted therethrough or reflected therefrom.
Another object of the present invention is to provide an actively-controlled window or viewing panel constructed from the electro-optical glazing structures of the present invention, wherein only UV and IR radiation is reflected at the window surface, while electromagnetic radiation over the visible band is transmitted to the interior environment being maintained under thermal control.
Another object of the present invention is to provide an intelligent window system for installation within a house or office building, or aboard a transportation vehicle such as an airplane or automobile, wherein the electro-optical glazing structure thereof is supported within a prefabricated window frame, within which are mounted: a electromagnetic-sensor for sensing electromagnetic conditions in the outside environment; a battery supply for providing electrical power; a electromagnetic-powered battery recharger for recharging the battery; electrical circuitry for producing glazing control voltages for driving the electrically-active elements of the electro-optical glazing supported within the window frame; and a micro-computer chip for controlling the operation of the battery recharger and electrical circuitry and the production of glazing control voltages as required by a radiation flow control program stored within the programmed microcontroller.
A further object of the present invention is to provide such an electro-optical window structure which is designed for integration within the heating/cooling system of a house, office building, factory or vehicle in order to control the flow of broad-band electromagnetic radiation through the electro-optical window structure, while minimizing thermal loading upon the heating/cooling system thereof.
Another object of the present invention is to provide a thermal/viewing shield or panel made from electro-optical glazing structure of the present invention.
Another object of the present invention is to provide of an intelligent pair of sunglasses, in which each optical element is realized using an electro-optical glazing structure of the present invention, fashioned to the dimensions of a sunglass frame.
Another object of the present invention is to provide of an intelligent pair of shutter glasses, in which each optical element is realized using an electro-optical glazing structure of the present invention, fashioned to the dimensions of a shutter glass frame.
Another object of the present invention is to provide an intelligent windshield or viewing screen, which is realized from an electro-optical glazing structure of the present invention.
These and other objects of the present invention will become apparent hereinafter and in the Claims to Invention.